Can't get past authentication screen

When I launch Starcraft 2 the game crashes during the “Authentication” screen with the message: “Files in your StarCraft II installation are damaged”. This only occurs when I try to log in to EU servers. NA and KR work just fine. I also newly created another battle.net account, and I can log in to EU servers on that without any issues. The issue is clearly not on my side, my files are not damaged.

I’ve submitted two tickets already and received irrelevant automated replies—one about Warcraft 3, the other about Starcraft Remastered. Neither about my actual issue.